The purpose of the Body Weight Regulation Core (BWRC) will be to provide state-of-the-art techniques to assess body weight regulation in the mouse, including the effects of body weight- lowering strategies such as exercise, diet restriction, and bariatric surgery. The services proposed by the BWRC have been exquisitely refined to make precise measurements and perform sophisticated procedures. The indirect calorimetry system we employ is the most advanced system available and yields exquisite behavioral details related to energy balance (energy expenditure, physical activity, food intake, water intake) with high temporal resolution. To complement whole body indirect calorimetry and exercise studies, we will offer high- resolution assessment of mitochondrial respirometry and reactive oxygen species emissions at the tissue, cell, and mitochondrial levels. This will allow the investigator to determine whether differences in whole body energy balance are associated with mitochondrial dysfunction. The BWRC will provide four distinct bariatric surgery procedures that closely mimic those performed in humans: Vertical Sleeve Gastrectomy, Roux-en-Y Gastric Bypass (modified for the mouse), Biliopancreatic Diversion and Biliary Diversion. These unique procedures allow the investigator to address questions about gut function and the contribution of the gastrointestinal tract to metabolic state. We also provide telemetry services for the assessment of cardiovascular function in conscious free-roaming mouse. The close relationship that the BWRC will maintain with the Metabolic Regulation Core will provide an extremely thorough phenotyping platform. The BWRC will provide highly advanced technology to comprehensively phenotype body weight regulation in mouse models.